The New Delhi office was set up during 1949 as the AMD headquarter, which was shifted to Hyderabad in 1974 and the office at New Delhi remained as the regional headquarter for Northern Region. Rajasthan was initially a part of the Northern Region, but during 1988 it was included in the newly created North-western Region. (Now Western Region).
The Northern Region comprises of Great Himalayan mountain ranges exposing igneous and metasedimentary rocks of various ages in the Higher and Lesser Himalayas, the trans-Himalayan sedimentaries, the Siwalik sediments, the vast Gangetic alluvial tract and the Archaean granitoids and Proterozoic sediments in the south.
(i) The Higher Himalayas : comprises of granite gneisses and high grade metamorphic rocks, also known as the Central Crystalline. To the south, across the Main Central Thrust (MCT), the Lesser Himalayas are represented by metasedimentary and metabasic rocks with some well-known nappes and klippes, with or without intrusive granites. The Main Boundary Thrust (MBT) separates the Lesser Himalayan rocks from the Siwalik belt.
(ii) The Siwalik belt : extending from Jammu & Kashmir through Himachal Pradesh to Uttarakhand is a prominent geological feature of the Region. The Siwalik sediments are divided into Lower Siwalik (mainly argillaceous), Middle (arenaceous with shale inter layers) and Upper Siwalik (conglomerates with sandy lenses)
(iii) The Himalayan Frontal Fault (HFF) to the South separates the Siwaliks from the Indo-Gangetic plains.
Further south of the Indo-Gangetic plain, the Proterozoic Bijawar-Gwalior-Vindhyan Groups of rocks are exposed over the Bundelkhand Granitic Complex, which forms the basement. The southern margin of the Vindhyan basin is bound by the Mahakoshal Group and Chhotanagpur Granite Gneisses.
Although no economically viable deposits have been found so far, significant uranium occurrences have been discovered at many places in almost all geological domains of the Northern Region.
The Siwalik sediments due to their sedimentological character, provenance and depositional environment have been considered as favourable host for epigenetic sandstone-type of uranium mineralization. Investigations carried out by AMD in Siwaliks since 1969 in different phases, have resulted in discovery of many uranium occurrences from Jammu & Kashmir in the northwest to Uttar Pradesh and Uttarakhand in the south-east.
Lenticular uraniferous zones extending from tens to hundreds of metres in dimension with low average grade have been found over large areas in both sandstone and conglomerate in the Upper-Middle Siwalik transition zones of Himachal Pradesh, Haryana, Uttarakhand and Jammu and Kashmir. Low grade lenses up to hundred meters have been found and exploratory drilling was carried out in many places. Exploratory mining was done in three blocks viz. Astoth, Khya and Andalada in Hamirpur district, Himachal Pradesh. Important Uranium occurrences are established in Rajpura in Una district and Loharkar in Hamirpur district. Other similar occurrences are found in Danaur and Naugajia Rao-Shakambari Rao Uttarakhand, Maler and Thein, Jammu and Kashmir and Morni, Haryana.
In the pre-Siwalik Tertiary sediments also, a number of uraniferous anomalies have been located in the Dharamsala Group of rocks in Solan and Mandi Districts, H.P., out of which Tileli is the largest occurrence so far identified. At Tileli, uranium mineralisation associated with lithic arenites at the contact of Lower & Upper Dharamsala formations, was located over a zone of 500m x 10m and its persistence to a vertical depth of 300m has been probed by exploratory drilling.
The gneissic rocks of the upper Himalayas show extensive development of secondary minerals, for example, at Chaura in the Kinnaur district of Himachal Pradesh, where significant uranium mineralization has been located in the sheared gneisses and quartzites of the Rampur Group along the Main Central Thrust (MCT. The important sites are Kasha, Kandi and Kaladi in Shimla district of Himachal Pradesh. This mineralization occurs as small veinlets. Yellow cake has been obtained from uraninite veins (veinlets) of Kandi area by small scale mining and heap leaching.
Similar uranium occurrences have also been located in Berinag Quartzite of Uttarakhand. Shear/fracture - controlled uranium mineralization of significant dimensions and grades is hosted by chlorite-sericite schists in Pokhri area of Chamoli district and in granite gneiss in Brijranigad area of Tehri district of Uttarakhand. Exploration work in the Himalayas has been largely hampered due to geological complexities and lack of infrastructure facilities.
Metamorphite-type low-grade uranium occurrences have been established in many places in Sonbhadra district of Uttar Pradesh, such as Naktu, Kudar, Nawatola, Satbahni-Murratola, Kudri and Anjangira areas. The host rock is mostly feldspar rich Pegmatoidal Leucosome (PL) and to a lesser extent, Biotite Melanosome (BM), both comprise the prominent proportion of the migmatites of Chhotanagpur Granite Gneiss Complex (CGGC).
Low-grade uranium mineralisation associated with fracture-filled bitumen in chloritic shale, Bandai Sandstone and Rohini Carbonate of Bijawar Group around Sonrai, Lalitpur district, Uttar Pradesh.
Several uranium occurrences have been located at the unconformity contact between the Proterozoic cover of rocks (Vindhyan/Gwalior) and Bundelkhand Granite Complex (BGC) in Doha, Dursendi and Mahrampur areas of Gwalior district, Madhya Pradesh. Promising zone of albitite-hosted uranium occurrences similar to Rohil deposit are also under exploration in north-eastern parts of North Delhi Fold Belt (NDFB) in Dochana, Mohanpura and Rambas areas, Mahendragarh district, Haryana.